When I did my sprayer training the instructor gave us a couple of 'working out application' sheets and told us to photocopy a heap of them. He said to write the date on one and bung it in the the big table diary whenever we used chemicals to aid the smooth passage of any inspections along with what we wrote in the spray record book. Those copies and blanks are invaluable for working out rates and using as a simple crib sheet for future applications. The spray record book doesn't tend to hold data in as convenient a reference form and doesn't include your working out formulae. Being able to prove competence may be invaluable in the event of a dispute with neighbours or the authorities and safety checks and monitoring are only going to get more onerous.